msgflo-python: Use python in hashbang, == py3

Author: jonnor

bin/msgflo-python

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python
 
 import sys, os, importlib
 sys.path.append(os.path.abspath(".."))
@@ -25,7 +25,7 @@ def main():
     prog, args = sys.argv[0], sys.argv[1:]
     try:
         modulepath, role = args[0:2]
-    except ValueError, e:
+    except ValueError as e:
         sys.stderr.write("Usage: msgflo-python MODULE.py ROLE\n")
         return 1